Referring to FIG. 9, a ratchet wrench 102 of the prior art comprises a handle 104 and a head section 106 further including a ratchet wheel 108, a claw piece 110, an inverting piece 112 and a rotational switch 114. Thereby, a user can twist the rotational switch 114 so as to switch the claw piece 110 to either the left side or the left side of the ratchet wheel 108. Therefore, the wrench can either fasten or loosen a screw bolt or nut (not shown in the figure).
Referring to FIG. 10, another ratchet wrench 116 of the prior art comprises a handle 118 and a heat section 120 further including a ratchet wheel 122 and an inverting piece 124. The inverting piece 124 being an elongated bar has a central notch with a right teeth section and a left teeth section (126), whereby the inverting piece 124 can be shifted transversely to have either one of the teeth sections to engage with the ratchet wheel 122. Therefore, the wrench can either fasten or loosen a screw bolt or nut (not shown in the figure).
Referring to FIG. 11, a third ratchet wrench 128 of the prior art comprises a head section 132 and a handle 130; there is a ratchet wheel in the head section 132, which is not shown in the figure. The head section 130 further includes a claw piece 136, an inverting piece 138 and a switch 140 having a central portion pivotally connected to the head section 132, whereby either of two ends of the switch 140 can be pressed so that the inverting piece 138 housed within a front hole 142 of the switch 140 can drive the claw piece 136 to engage with the ratchet wheel to restrict its rotation in one direction. Therefore, the wrench can either fasten or loosen a screw bolt or nut (not shown in the figure).